Abstract: In this study,the effects of thermosonication (TS) treatment on inactivation of naturally occurring microorganisms and quality retention in fresh red dragon fruit juice were investigated,with fresh and heat treated (95℃,10 min) juice as controls. The results showed that,the increasing of in-put power and temperature or prolongation of treatment time had facilitat effective control on naturally occurring microorganisms,while negatively affected color,retention of V_C and total sugar. There were insignificant difference in soluble solid content,pH and total acid contents of fresh red dragon fruit juice during TS treatment with fresh juice (p>0.05). For instance,the number of aerobic bacteria of reduced to 1.77lgN,and that of yeast and molds reduced to under the detection limit as fresh red dragon fruit juice was exposure to TS treatment at 570 W and 50℃ for 30 min. In this case,its color was retained closing to fresh juice without visual color difference (ΔE^*<2),and 86.89% V_C and 87.04% total sugar contents of fresh juice was retained,respectively. However,naturally occurring microorganisms in fresh red dragon fruit juice were effective inactivated under heat treatment (95℃,10 min),an unacceptable deterioration and significant change in juice quality of color,retention of V_C and total sugar was observed. Therefore,TS treatment at 570 W and 50℃ for 30 min might be recommended for fresh red dragon fruit juice processing.